Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$184.59	7.303%	$198.0706	$198.07	$198.05	$198.10
Purchase #2	$190.91	9.416%	$208.8861	$208.89	$208.90	$208.90
Purchase #3	$248.54	10.450%	$274.5124	$274.51	$274.50	$274.50
Purchase #4	$10.27	3.837%	$10.6641	$10.66	$10.65	$10.70
Purchase #5	$86.88	3.173%	$89.6367	$89.64	$89.65	$89.60
Purchase #6	$15.68	4.724%	$16.4207	$16.42	$16.40	$16.40
Purchase #7	$245.90	13.835%	$279.9203	$279.92	$279.90	$279.90
7 purchase totals =	$982.77		$1,078.1109	$1,078.11	$1,078.05	$1,078.10